I have several times referred to my DIY gravity water filter. It's lighter than any pump filter and most gravity setups, and no pumping is needed. I finally located my parts list, so I can furnish the how-to information. I'll add pictures of my setup later, but in the meantime, here's a link to pictures of a similar setup: There are several DIY gravity filters described in this BPL thread. The one I made is shown most of the way down on page 2, the post by Cola Vaughan showing the bright orange silnylon bag.

Parts:

Katadyn Hiker Pro replacement filter cartridge

Bag to hold the dirty water, Sea-to-Summit Ultra-Sil dry bag, 8 liter. I don't fill it full, no more than 4-5 liters at a time. I hang it by the loop formed by the dry bag closure.

2 flat rubber washers with 3/8" or 1/2" hole, from hardware store, Lowe's or Home Depot

4 feet of cord to tie dry bag closure loop to a tree should you be in a heavily used campsite with large old growth trees and no lower branches or even stubs of branches. I've had to do this only a few times in the last 5 years, but the cord was desperately needed at those times!

First, trim most of the unneeded plastic housing off the Katadyn Hiker Pro filter cartridge, being sure to leave the nozzle intact. This will lighten the filter weight by about an ounce. Not having the recommended Dremel tool, I used an old kitchen knife, heated on the stove burner, which worked better than a hacksaw. Before trimming, I put a short piece of plastic hose over the nozzle opening of the filter to protect it, and was super careful not to let the hot knife touch that vital part. Don't expect to have a pristine butcher knife afterwards! In the grand scheme of things, this step may not be worth the ounce of weight saved!

I used a piece of metal (actually the round handle end of an all-metal whisk, about 1/2" in diameter) to melt a hole in the bottom of the dry bag, and then coated the area around the hole with McNett Silnet. (What I didn't do, and should have, was to put the hole at one side of the bottom so the filter will lie flat in the bottom of the bag.) With the flat rubber washers on each side of the hole, fasten together the male and female adapters, one on each side of the hole. Cut a short (2 1/2 inches) piece of plastic tubing to connect the filter cartridge nozzle to the adapter nozzle inside the bag. Cut 3 feet of tubing to connect the adapter nozzle on the outside the bag to your clean water container. Thread the long piece of tubing through the clamp so you can start and stop the water flow from the filter. Test the setup in your bathtub or shower stall. A new filter will bleed carbon dust the first time it is used, so let the water run through until it is clear--do this before your first trip.

If you still have a (now discontinued) Platypus filter connector, you can connect it to the other end of your tubing--the Platy top fits soda water bottles, Evernew bottles and, of course, Platy bottles. At present, the only way to get such a connector is to buy a Platy tube kit. Platypus tubing is heavier and much stiffer than the nice flexible tubing from US Plastics, so remove the Platy tubing and just use the bottle top and connector.

The Katadyn Hiker Pro filter cartridge has two advantages: It has a built in prefilter covering wrapped around the filter, which can easily be removed and rinsed, and it contains activated charcoal which helps remove bad tastes. The charcoal isn't enough to remove chemical pollutants in the water, though. If the water is really nasty, you will need an additional prefilter, such as a bandanna or coffee filter.

I've used this setup for the past two years. It works quite fast, taking about 10 minutes to filter 5 liters of water. For mid-day refills, you can easily filter 2 liters during a 5-minute rest/snack period.

The most wonderful thing about this setup is that you no longer need to stand or sit alongside a buggy stream pumping away! You fill the bag, carry it to camp and hang it up, connect it with your water bottle, undo the clamp and then do other chores while the water is filtering. You do have to keep an eye on the process to avoid overflowing or having the water flow stop when air pressure builds up in your clean water container. This setup is wonderful for small groups because you can filter up to 1 1/2 gallons at a time.

Dry weight of my setup is 6.6 oz. (includes the Platy filter connector but not the cord). I need to weigh it wet, since that's how it will be for most of a trip, and will add that information later along with photographs.

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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey

The filter can be backflushed by blowing a tube full of filtered water back through the filter. I also blow into the clean end of the system when packing up to remove as much water as possible from the filter.

When you say blow a tube full of water, are you blowing it by mouth or is this with a compressor at home or am I missing the meaning entirely?

No, this is putting the clean end of the tube in my mouth and huffing and puffing a couple of times. That's with the empty bag (with filter inside) hanging upside down. I've gotten as much as half a cup of water out of the filter by doing that.

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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey

I actually just purchased my first gravity filter two nights ago. It is currently en route. I am excited to get it and use it just because I know I am going to smile so wide when I am filtering water as I sit in my chair watching everyone else pump theres....hahahaha!

I purchased a Seychelle Gravity filter system for cheap...as seen here.

Ya got me thinkin here. Smell the smoke. I like this idea somewhere I have one of those cheap 8.00 wally world camp solor showers with the hose already coming out of it. I have to find it and see what it weighs! I thought maybe my sea to summit backpacking shower might work? But the nozzle doesnt come off the bag. That water filter could double as a solar shower very nice as well. I am gonna see what I can come up with in the morning. Thanks for posting this, I like it! I hate pumping my current Katadyne filter.

The pinch style tube clamps for shutting off flow tru the hose are available at most local wine making shops. I use one myself when bottling wine. For tubing clams to fittings I use small zip ties. Most fittings to make one are available at a home center store. I think I will go shoping and see what I can find.

I have, as suggested earlier, removed the Katadyn Hiker Pro filter and spliced in the Sawyer Inline filter external to the bag. Works fine! While i use the Sawyer Squeeze when solo, this version is better for groups.

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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey

I have, as suggested earlier, removed the Katadyn Hiker Pro filter and spliced in the Sawyer Inline filter external to the bag. Works fine! While i use the Sawyer Squeeze when solo, this version is better for groups.

Do you put the filter close to the exit of the hose, or close to the dirty bag?

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I've taken a vow of poverty. To annoy me, send money.

Worked just fine with the Katadyn filter in the bag. That's the same configuration as my modle, the late lamented ULA gravity filter. For the Sawyer Inline, I have it spliced in the outlet hose about 2 feet below the dirty bag.

After my Sawyer squeeze turned out to be completely blocked this week, even though I had tested it with tap water at home the week before, I'm becoming a bit disenchanted with Sawyer, though. Spending two days boiling water for two, a liter at a time (I had enough so I didn't have to boil today), instead of fishing. was not my idea of fun!

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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey

I usually do, but I hadn't checked my first aid kit before the trip. Turned out I must have removed them. Lesson learned the hard way! I did take extra fuel because it was a fishing trip, but only one of the fish my grandson caught was a "keeper." For him the trip was a success because it was his first trout, on a brand new fly rod.

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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey

Mary, after you posted on your setup I tried putting my Sawyer on the end of the tubing coming from my Amigo Pro setup (with the original filter removed). That worked quite well, so I have ordered one of the S to S dry bags, and will probably move the Amigo connectors and tubing over to that bag to mimic your system, since the Amigo bag has sprung some leaks and is not that easy to fill from lakes anyway. Thanks for the idea! (I will make sure to always bring the syringe to backwash...)